Heater for traveling stock



M 7, 1932. E. F. NORTHRUP 1,862,120

HEATER FOR TRAVELING STOCK Filed Sept. 5, 1929 Patented June 7, 1932 UNITED STATES PATENT OFFICE.

IIElDWIlSl FITCH NORTHRUI, OF PRINCETON, NEW JERSEY, ASSIGNOR TO AJAX ELECTRO- THERMIC CORPORATION, OF AJAX PARK,

PORATION OF NEW JERSEY EWING TOWNSHIP, NEW JERSEY, A GOR- HEATER FOR TRAVELING STOCK Application filed September 3, 1929. Serial No. 389,889.

The invention relates to the electrical heating of pipes.

One purpose of the invention is to electroinagnetically float a core of magnetic material within a pipe which is being heated by the passage of electric current about the pipe, using either solenoid or electromagnetic means.

A further purpose is to electromagneticall y position a magnetic pipe core for use within an electric circuit heating a pipe which surrounds the core, using electro-magnetic positioning means also for a return circuit for the magnetic lines passing through the core.

Further purposes will appear in the specification and in the claims.

I have preferred to illustrate my invention by several forms only, of many in which the invention may appear, selecting forms which are simple, reliable, practical and efficient and which at the same time well illustrate the principles thereof.

Figure 1 is a longitudinal sectional View of one means for applying my invention.

Figure 2 is an enlarged longitudinal section corresponding generally to Figure 1 but showing an additional magnetic circuit.

Figure 3 is a section of Figure 1 taken upon line 3-3 and looking in the directionof the arrow.

Figure 4 is a longitudinal section of a structure in which the holding means and the return circuit of Figures land 2 are combined in one structure.

Where pipe shown generically at 10 is to be heated by any coil 11 while the pipe is passing through the coil, the depth of penetration of the induced current within the pipe varies inversely as the square of the frequency. It is desirable that the question of selection of the frequency shall be freed from consideration of pipe thickness and for this reason it is advantageous to utilize a core preferably of magnet-izable material inside of the pipe at the point where it is surround ed by the heating coil. Non-magnetic pipe can be heatedwith lower frequencies if such an iron corelQ be used than would otherwise be ell'ect1v e.:=" The core 1s preferably made of nichrome or of a steel which has a high recalesc'ence point.

The core may be solid or laminated; but since the heating of the core may be utilized to heat the pipe from the inside individual installations may derive little advantage from lamination of the core.

' My present invention preferably uses high frequency which has marked advantages due to the high rate of change. These are not fully ofiset by the advantage of lower fre quencies from the greater ease of obtaining current supply.

The heating coil 11 or 11 is shown in F igures 2 and 4 as an edgewound hollow coil adapted to be water-cooled. but evidently the invention would apply with coils of other character, whether water cooled or not, and without regard to the edge winding.

Where the temperature of the core is not intended to exceed about 675 C. a much lower frequency may be used to advantage than could be used for higher temperatures, utiliz ing the magnetic properties in the .core to improve the magnetic circuit of the coil 11 or 11 up to this temperature. However. when; the temperature is intended to exceed the recalescence point of iron it makes very little difference whether iron or some other material be used for the core, but the frequency should be made relatively high in order to heat the iron within its non-magnetic range or to heat theother metal throughout the required range.

This application is a continuation of my application. Ser. No. 76.878. filed December 21, 1925. insofar as the subject matter of Figure 1 is concerned, which subject matter is shown in Figure 10 of the above application.

In Figure 1 the core 12 will be of magnetic inaterial unless the intended temperature to which it. is to be raised is above the recalescenee point for nichrome or steel. The core is held within the heating coil 11 by the effect upon an armature 13 of a direct current passing through a solenoid 14 and indicated diagraunnatically as supplied from a battery 15.

'lhe solenoidal armature 13 is connected with the heating core as by a rod 17.

In operation the pipe to be heated is moved continuously at a rate of speed determined by the rate of heating effected by the current induced within the pipe and by the heat produced within the core. The latter is more efficient than would otherwise be the case because it heats from the inside of the pipe and no heat can escape from it except into the pipe.

For use where the temperature of the core 12 is to be raised to less than the recalescence point'the presence of a magnetic core within the coil tremendously improved the coupling of the coil which, however, in the form of Figure 1 must find its magnetic return circuit though the air from the ends of the core back outside of the coil.

In the form shown in Figure 2 I have continued the advantage for non-magnetic piping of having solenoidal holding of the core within the heating coil and have added a feature which is of advantage whether there be a core or not and whether thepipe be of magnetic material or not, in the magnetic return effected by preferably laminated iron strips 18 about the coil 11. Their poles 19 are turned toward the pipe. Any suitable number of these strips can be used, distributed about the coil to afford such approximation to a complete return magnetic path as is deemed expedient by the designer. Two sets or groups of laminated return plates only are shown in Figure 3.

It will be evident that the coil of Figures 2 and 3 is provided with a Very complete magnetic return when a core 12' of magnetic material is used within it, and that the magnetic return of the coil is improved in any event by the outside return path.

In Figure 4 the electromagnetic retention of the core within the coil for use with nonmagnetic pipe is secured by using the magnetic return circuits 18 as electromagnets by supplying them with windings 14' tending to set up magnetic flux in them. The direct current for these windings 14' is supplied by a battery 15' and flow of current induced by the return flux from the heating coil is prevented by the use of a choke coil 20.

It will be evident that the electromagnetic core holding mechanism is desirable whenever the pipe is of non-magnetic material; and that the use of a magnetizable core for high frequency is advantageous with any non-magnetic pipe and with pipe of mag netic material if the pipe be too thin to well carry the magnetic flux.

Where the pipe isv thin so the depth to which current induced by the coil tends to flow is greater than the depth of the pipe, even a non-magnetic core wouid carry induced current and would offer advantage in permitting the use of a lower frequency, if desired, than could well be used otherwise.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is 1- 1. In inductive heating,an inductor coil adapted to heat a tubular article within it, in combination with an iron core, adapted to lie within the article and coil, an armature secured to the core and a solenoid for anchoring the core to permit movement of the tubular article without disturbing the core.

2. In a heater for pipes, a heating coil about the pipe and adapted to receive alternating current, a floating core within the pipe and an electromagnetic holder for the core adapted to position the core within the coil.

3. In a heater for travelling pipe, 21. heating coil surrounding the pipe, a floating core within the pipe adapted to lie within the coil, a solenoidal coil, a solenoidal armature therefor connected to the core within the heating coil and a source of direct current supply for the solenoid.

4. In a heater for travelling pipe, a heating coil, an alternating current source of supply therefor, a magnetic core within the coil and electromagnetic means for holding the core within the coil comprising in part return circuit for the magnetic lines from the heating coil.

5. In a heater for travelling pipe, a coil adapted to surround the pipe, a source of alternating current supply therefor, a magnetizable core within the pipe and coil, magnetic return material for the coil located outside of the coil and having terminals in proximity to the pipe, a winding about said magnetic return material and a source of direct current for said winding.

6. In a heater for travelling pipe, a coil adapted to surround the pipe, a source of alternating current supply therefor, a magnetizable core within'the pipe and coil, mag netic return material for the coil located outside of the coil and havin terminals in proximity to the pipe, a winding about said magnetic return material, a source of direct current for said winding and a choke coil within the circuit of said winding to protect against induced flow of current therein.

7. In a heater-for travelling pipe, a coil about the pipe adapted to receive alternating current,'a core within the ipe and electromagnetic holding means or said core spaced along the pipe from the coil.

8. In a heater for travelling pipe, an alternatin current heatin coil adapted to surroun the pipe, an a ternatin Y current supply therefor, a core, magnetiza le material within the coil spaced from the core and a combined return magnetic circuit outside of the coil and electromagnetic holder for the core so that the core floats within the pipe at the coil position.

'9. In a heater for travelling ipe, electromagnetic heating means for t e pipe Sm rounding the pipe and an inductively'heated core within the floated within the pipe.

10. In a heater for travelling pipe, a coil about the ipe, a high frequenc current supply there or and an electrical y conducting core within the pipe and coil.

11 In a heater for travelling pipe, a coil about the ipe, a high frequency current s ply there or and a magnetic core within ta 7 pipe and coil.

12. In a heater for travelling stock, a stock surrounding coil, a magnetic return circuit so Y outside of the coil and extending lengthwise of the stock, a winding ininductive relation to the return circuit to cause ma etic flux in the return circuit in the same direction as the flux of the return circuit and a source of current for said windin EDWIN rrrdii NORTHRUP.

pipe electromagnetically 

